Who is Constance Ogden from A Lost Lady and what is their importance?

Constance Ogden is the young woman who visits the Forrester family in Sweet Water. Mrs. Forrester employs Niel to keep Constance company, hoping that she will fall in love with Niel and forget Frank...... Mrs. Forrester's lover. Over time, however, Constance wins Frank Ellinger and marries him several years later.